Re: Passing strings between a vc6 dll and vb6 exe

From:

"Brian Muth" <bmuth@mvps.org>

Newsgroups:

microsoft.public.vb.general.discussion,microsoft.public.vc.language,microsoft.public.vc.mfc

Date:

Mon, 2 Jun 2008 16:28:27 -0700

Message-ID:

<OQiRdhQxIHA.1440@TK2MSFTNGP05.phx.gbl>

You are trying to pass the address of the string across process boundaries. This is pointless, since the address is meaningless to
the target process since every process has its own address space.

Using DCOM would be the best solution here. Your VB6 executable should be created not as a "Standard EXE" but an "ActiveX EXE". You
can then define a class module that can be instantiated by the C++ code as a remote object, and call the functions you define,
including one that presumably takes the string as a parameter.

Unfortunately, the learning curve here is pretty significant, and I'm wondering if you would consider turning to a colleague or
outside professional with DCOM experience to cruft this up for you. Otherwise, you will have weeks, if not months of work ahead of
you.

(my $0.02)

<santosh.pjb@gmail.com> wrote in message news:5f3dff75-16c9-4a7d-b0d3-f5912b583471@w34g2000prm.googlegroups.com...

I have a win32 dll (VC6) and a VB6 exe. The dll gets loaded (and a
specified single parameter function is called) by a 3rd party app -
when an event of interest occurs. The 3rd party app uses the __cdecl
calling convention and passes a single LPSTR argument to the dll
funtion. I now want to add some code in that dll fn to pass the string
to the VB exe.

I haven't done much win32 programming recently and more importantly
haven't touched VB in nearly a decade so looking for some advice on
how to proceed.

After a bit of googling, I decided to use FindWindow() and
SendMessage() on the VC dll side, and subclassing the WindowProc on
the VB side to receive the message.

This seems to be working as the VB exe receives the message, but it
doesn't receive the string being passed or to be more specific it
recieves a pointer to some garbage.

This is what the code looks like
VC6 DLL :-
long foo(LPSTR id){
      FindWindow(NULL,"VBApp")
      char cTemp[50];
      strcpy_s(cTemp,cid);
      h = FindWindow(NULL, "Parse");
     SendMessage(h, WM_USER + 234, NULL, (LPARAM) &cTemp);
}

VB exe :-
WindowProc(...)
If (uMsg = WM_USER + 234) Then
       sLen = lstrlen(lParam)
       sString = Space$(sLen)
       CopyMemory ByVal sString, ByVal lParam, sLen
       DebugPrint ("Received: " & sString) << ====== Prints garbage
       DoSomething(sString)
End If

CopyMemory is kernel32 RtlMoveMemory

Any advice is greatly appreciated,
Thanks